Aseptic loosening continues to be a problem with total hip replacements. In cemented total hip replacement, mechanically induced loosening most often initiates at the stem-cement or cement-bone interface. And while it is widely accepted that a strong bone is desirable at the cement-bone interface, the optimal cement-metal interface is disputed for cemented femoral components. A research program is proposed to investigate: 1) the specific mechanical conditions under which the femoral stem-cement and cement-bone interfaces fail; 2) the manner in which interface failure contributes to mechanical loosening of cemented femoral hip components; and 3) the use of this information to "optimize" the locations and extent of stem-cement bonding to reduce the risk of implant failure. Here, "bonding" is used to describe any enhanced stem-cement interface (mechanically roughened or PMMA precoated), as compared to a smooth unbonded interface. It is the hypothesis of this work that the manner and extent of bonding of the stem-cement interface affects the overall failure (loosening) of the implant. It is further hypothesized that some "optimum" configuration, consisting of regions where the stem is bonded, and regions where the stem is unbonded, will result in a significant increase in the long-term performance of the implant.